Saturday, May 01, 2021

CDC Update: COVID-19 Vaccine Breakthrough Cases (Apr 30th)


Unlike currently hard-hit regions of the world like India and Brazil, the United States continues to see a welcomed drop in COVID cases (see chart above), likely due in large part to the fast-paced rollout of COVID vaccines. 

Although fewer people may be seeking out testing when symptomatic, more than 100 million Americans (30.5%) are now fully vaccinated, and another 43 million have received at least one dose. 

Daily vaccine uptake, however, has dropped (see chart below) roughly 40% since early April, raising concerns that vaccine hesitancy. or complacency in the face of shrinking case numbers, is taking its toll.  

Although no vaccination is 100% effective in 100% of its recipients, the three approved COVID vaccines in the United States have shown remarkable effectiveness.  The CDC announced earlier this week that:

Fully Vaccinated Adults 65 and Older Are 94% Less Likely to Be Hospitalized with COVID-19

CDC Assessment Finds mRNA COVID-19 Vaccines Reduce COVID-19-Related Hospitalizations Among Older Adults

Press Release

For Immediate Release: Wednesday, April 28, 2021
(404) 639-3286

Both mRNA COVID-19 vaccines (Pfizer-BioNTech and Moderna) authorized and recommended in the United States protect against COVID-19-related hospitalization among adults 65 years and older, according to a new CDC assessment that finds fully vaccinated adults 65 years and older were 94% less likely to be hospitalized with COVID-19 than people of the same age who were not vaccinated. People 65 and older who were partially vaccinated were 64% less likely to be hospitalized with COVID-19 than people who were not vaccinated. People were considered “partially vaccinated” two weeks after their first dose of mRNA vaccine and “fully vaccinated” two weeks after their second dose.

These are the first real-world findings in the United States confirming clinical trial data showing mRNA vaccines prevent severe COVID-19 illness. The findings provide additional support for CDC’s recommendation for COVID-19 vaccination among people 65 and older in the U.S. population under the Emergency Use Authorization (EUA) for the applicable COVID-19 vaccine as the risk for severe illness with COVID-19 increases with age, with older adults at highest risk.

While there remain open questions about how long vaccine protection will last, and how well current vaccines will fare against some of the new emerging COVID variants, the concurrent drop we've seen in hospitalizations and deaths in countries with successful COVID vaccination campaigns is impressive. 

Even in cases where they don't prevent infection, there is some evidence to suggest that COVID vaccines may reduce the severity of illness, and that should translate into fewer hospitalizations and fewer deaths. 

When you vaccinate 100 million people with a a vaccine that is - at best - 90% protective against infection, you are going to see a fair number of breakthrough infections.  Millions of vaccinated people are still going to become infected, although most will likely see a milder course of illness due to the vaccine. 

Nearly 3 weeks ago, in CDC: COVID-19 Breakthrough Case Investigations and Reportingwe looked at the CDC's first weekly update on COVID-19 Breakthrough cases in fully vaccinated individuals, as reported by state and local health departments.

While it is undoubtedly a substantial undercount, as of April 26th the CDC has been notified of 9,245 breakthrough cases - a roughly 58% increase over their initial report of April 13th.

This is a remarkably low number - and even though it is likely to rise markedly in the weeks and months ahead - should be viewed as a positive sign. But it is a reminder that vaccination is not an ironclad guarantee of protection.

Hence the need for vaccinated individuals to continue to observe some of the same social distancing measures as those who remain unvaccinated (see CDC Guidelines on How Fully Vaccinated People Can Visit Safely with Others).

While I'm far from convinced we are out of the woods with the COVID-19 pandemic, or that the current vaccines will be enough to vanquish the virus, I am heartened by the results we've seen to date. Even with their limitations, I'm thankful to have received both doses of the mRNA vaccine. 

Some excerpts from the CDC's latest Vaccine breakthrough report follow, but click the link to read the report in its entirety.

COVID-19 Breakthrough Case Investigations and Reporting

This page provides information and resources to help public health departments and laboratories investigate and report COVID-19 vaccine breakthrough cases.

  • Vaccine breakthrough cases are expected. COVID-19 vaccines are effective and are a critical tool to bring the pandemic under control. However no vaccines are 100% effective at preventing illness. There will be a small percentage of people who are fully vaccinated who still get sick, are hospitalized, or die from COVID-19.
  • More than 95 million people in the United States had been fully vaccinated as of April 26, 2021. Like with other vaccines, symptomatic vaccine breakthrough cases will occur, even though the vaccines are working as expected. Asymptomatic infections among vaccinated people also will occur.
  • There is some evidence that vaccination may make illness less severe.
  • Current data suggest that COVID-19 vaccines authorized for use in the United States offer protection against most SARS-CoV-2 variants circulating in the United States. However, variants will cause some of these vaccine breakthrough cases.


COVID-19 vaccine breakthrough infections reported to CDC as of April 26

As of April 26, 2021, more than 95 million people in the United States had been fully vaccinated against COVID-19. During the same time, CDC received reports of vaccine breakthrough infections from 46 U.S. states and territories.

*241 (29%) of the 835 hospitalizations were reported as asymptomatic or not related to COVID-19.
†20 (15%) of the 132 fatal cases were reported as asymptomatic or not related to COVID-19.